Small Tentacles Research Articles

Development of the Visible‐Light Response of CeO2−x with a high Ce3+ Content and Its Photocatalytic Properties

AbstractPhotocatalysts that are responsive to visible light are necessary to utilize solar energy. We prepared reduced CeO2−x with absorption in the visible region by a simple solvothermal method. A new absorption band appearing at λ≈500 nm (surface plasmon resonance) could be ascribed to the high content of Ce3+. To elucidate the relationship between Ce3+ and activity, the decomposition of isopropyl alcohol (IPA) to generate acetone was performed under visible‐light irradiation. CeO2−x showed activity that was superior to that of pure CeO2. Ce3+ induced oxygen vacancies in the lattice of CeO2−x, and this resulted in an improvement in the activity. In addition, the introduction of Ce3+ resulted in an improvement in the absorption of CeO2−x in the visible‐light region. Also, the appearance of small tentacles (Confeito‐like) on the surface of CeO2−x not only provided more active sites but also prevented aggregation. Owing to its visible‐light responsiveness and unique morphology, the performance of this material was significantly improved relative to that of pure CeO2.

Pseudogramma polyacanthacomplex (Serranidae, tribe Grammistini): DNA barcoding results lead to the discovery of three cryptic species, including two new species from French Polynesia.

The Pseudogramma polyacantha species complex was found to harbor cryptic taxonomic diversity with three similar, but genetically divergent, species previously hidden in the complex. The true Pseudogramma polyacantha occurs from French Polynesia to South Africa and has modally 19 (many with 20) segmented dorsal-fin rays, modally 16 segmented anal-fin rays, a relatively short lateral line, no dermal flap or small tentacle dorsally on eye, and extensive scalation on the interorbital, suborbital and dentary. Pseudogramma brederi (previously synonymized with P. polyacantha) is recognized as a valid species occurring from Hawaii to Mauritius and having modally 21 segmented dorsal-fin rays, modally 17 segmented anal-fin rays, a relatively long lateral line, no dermal flap or small tentacle dorsally on eye, and relatively well-developed scalation on the interorbital, suborbital and dentary. Pseudogramma galzini n. sp. is described as a new species known only from French Polynesia and having modally 22 segmented dorsal-fin rays, modally 17 segmented anal-fin rays, a relatively long lateral line, no dermal flap or small tentacle dorsally on eye, and limited scalation on the interorbital, suborbital and dentary. Pseudogramma paucilepis n. sp. is described as a new species known only from French Polynesia and having 20 segmented dorsal-fin rays, modally 16 segmented anal-fin rays, a relatively long lateral line, no dermal flap or small tentacle dorsally on eye, and relatively reduced scalation on the interorbital, suborbital and dentary. A mtDNA COI analysis including all available Pseudogramma sequences shows well-supported genetic divergence between the two new species and among congeners.

Extraocular spectral photosensitivity in the tentacles of Hydra vulgaris

Previous electrophysiological studies on the cnidarian Hydra vulgaris have shown that hydra have a highly developed and specific photoresponse despite their lack of any structure recognizable as a traditional photoreceptor. In an effort to identify the site of hydra's photoreceptors, we recorded extracellularly from single excised tentacles and from ablated hypostomes lacking tentacles in absolute darkness and during exposure to light of various wavelengths. During recording, after an initial period of absolute darkness, tentacles or hypostomes were exposed to light from 450nm to 600nm, red, and white light. Exposure to light caused a change in the pattern and frequency of impulses in the tentacles that varied with color. The number of large tentacle pulses (TPs) increased at 550 and 600nm relative to darkness, whereas the number of small tentacle pulses (STPs) tended to decrease in 500nm light. Impulse frequency was significantly different among the different wavelengths. In addition to bursts of tentacle contraction pulses, long trains of pulses were observed. A change in lighting caused a switch from bursting to trains or vice versa. In contrast to excised tentacles, no change in electrical activity was seen in ablated hypostomes at any of the wavelengths relative to each other or relative to darkness. These results indicate that isolated tentacles can distinguish among and respond to various colors across the visible spectrum and suggest that electromagnetic information is transmitted from the tentacles to the hypostome where it may be integrated by the hypostomal nervous system, ultimately contributing to hydra's photoreceptive behavior.

Persica qeshmensis gen. nov. sp. nov from the Persian Gulf (Platyhelminthes: Polycladida: Acotylea), with remarks on reproductive structures

A new genus of acotylean polyclad, Persica qeshmensis gen. nov. sp. nov. (Acotylea, Pleioplanidae), was collected from intertidal rocky shores of the Northern Persian Gulf, Iran. The genus Persica is established on the presence of small tentacles; tentacular and cerebral eyes; spermiducal bulbs; true seminal vesicle; prostatic vesicle of atomata-type; muscular coiled ejaculatory duct, provided with a stylet, absence of a vagina bulbosa or Lang’s vesicle. Persica qeshmensis is characterised by a sandy beige to light brown background colour, with pale brown microdots, light grey ventral body surface, coiled ejaculatory duct embedded in parenchymatous cell mass, elongated sigmoid stylet, a well-developed penis sheath located in a small male atrium, and with a non-muscular blind chamber extending anteriad from the vagina to the level of the genital sucker.http://zoobank.org/urn:lsid:zoobank.org:pub:FAA7AA0A-6954-47D0-A5B2-1A2EC04050C3

Skin lesions in envenoming by cnidarians (Portuguese man-of-war and jellyfish): etiology and severity of accidents on the Brazilian coast

This work attempts to establish dermatological identification patterns for Brazilian cnidarian species and a probable correlation with envenoming severity. In an observational prospective study, one hundred and twenty-eight patients from the North Coast region of São Paulo State, Brazil were seen between 2002 and 2008. About 80% of these showed only local effects (erythema, edema, and pain) with small, less than 20 cm, oval or round skin marks and impressions from small tentacles. Approximately 20% of the victims had long, more than 20 cm, linear and crossed marks with frequent systemic phenomena, such as malaise, vomiting, dyspnea, and tachycardia. The former is compatible with the common hydromedusa from Southeast and Southern Brazil (Olindias sambaquiensis). The long linear marks with intense pain and systemic phenomena are compatible with envenoming by the box jellyfish Tamoya haplonema and Chiropsalmus quadrumanus and the hydrozoan Portuguese man-of-war (Physalis physalis). There was an association between skin marks and probable accident etiology. This simple observation rule can be indicative of severity, as the Cubozoa Class (box jellyfish) and Portuguese man-of-war cause the most severe accidents. In such cases, medical attention, including intensive care, is important, as the systemic manifestations can be associated with death.

The loricariid catfish genus Lasiancistrus (Siluriformes) with descriptions of two new species

Lasiancistrus (Loricariidae: Hypostominae: Ancistrini) is diagnosed by the unique presence of a ventral strut of the pterotic and the presence of whiskerlike odontodes on the snout. Lasiancistrus has about 16 species assigned to it; however, only four are valid (L. schomburgkii, L. caucanus, L. guacharote, and L. heteracanthus), L. nationi is an Ancistrus, and L. trinitatus is incertae sedis in the Loricariidae. Lasiancistrus maracaiboensis and L. mystacinus are synonyms of L. guacharote; L. pictus, L. castelnaui, L. caquetae, L. guapore, L. multispinis, and L. scolymus are synonyms of L. schomburgkii; and L. planiceps, L. mayoloi, and L. volcanensis are synonyms of L. caucanus. Two new species are described: L. tentaculatus from the río Orinoco basin and L. saetiger from the rio Guama. The species can largely be told apart via color (L. schomburgkii has no or white spots on the fins, L. saetiger has entirely gray fins, and the rest have black spots in the fins), the presence of abdominal plates (L. caucanus, L. saetiger, and L. tentaculatus have naked abdomens, L. guacharote has a few small plates near the insertion of the pectoral fin, L. heteracanthus has a large patch of small plates, and L. schomburgkii is variable), and nuptial male condition (L. tentaculatus has small tentacles along the edge of the snout and the other species have a patch of whisker-like odontodes at the corners of the snout). Most species are widespread in piedmont regions of South America with L. schomburgkii occurring in the Amazon, Orinoco, and Essequibo basins.

Photobehavior of stony corals: responses to light spectra and intensity

Tentacle expansion and contraction were investigated in four zooxanthellate coral species and one azooxanthellate coral (Cladopsammia gracilis). Favia favus, Plerogyra sinuosa and Cladopsammia gracilis expand their tentacles at night, while tentacles in Goniopora lobata and Stylophora pistillata are expanded continuously. Light at wavelengths in the range 400-520 nm was most effective in eliciting full tentacle contraction in F. favus and in P. sinuosa. Higher light intensities in the range 660-700 nm also caused tentacle contractions in F. favus. Tentacles in C. gracilis did not respond to light. Zooxanthellar densities in tentacles were significantly higher in G. lobata, which has continuously expanded tentacles, than in F. favus and P. sinousa, where tentacles are expanded at night. Photosynthetic efficiency in F. favus and P. sinuosa was lower in specimens with contracted tentacles. However, in the dark, no differences were found in the maximum quantum yield of photochemistry in PSII (Fv/Fm) of the expanded versus the contracted tentacles of any of the four species. This work suggests that species whose tentacles remain continuously expanded have either dense algal populations in their tentacles, as in G. lobata, or minute tentacles, like S. pistillata. Dense algal populations in tentacles allow harvesting of light while small tentacles do not scatter light or shade zooxanthellae in the underlying body of the polyp.

Effects of discharging nematocysts when an eolid nudibranch feeds on a hydroid

The exposure to discharging nematocysts of the eolid nudibranch Cratena peregrina feeding on polyps of the hydroid Eudendrium racemosum was examined. The smaller size-class of microbasic eurytele mastigophor nematocysts is located on the tentacles of the hydroid polyps, while the larger size-class of holotrichous isorhiza nematocysts is located on long cnidophores and basal rings of some polyps. Discharging nematocysts of the tentacles do not appear to have damaging effects on the dorsal appendages of the snail, the cerata. In contrast, contact of a cnidophore with a ceras elicits massive discharge of nematocysts, which results in adherence, membranolysis and local destruction of the epidermis within seconds. The differential locations and effects indicate that the small tentacle nematocysts serve for capturing prey, while the large cnidophore nematocysts serve for the hydroid's defence. Both small and large, discharged and intact nematocysts were found in the pharynx and stomach of the snail after feeding. Thus, the alimentary tract appears to be efficiently protected against discharging nematocysts. Small and large intact nematocysts, which were capable of discharge, were also found in the cnidosacs.

Expression and Developmental Regulation of the Hydra-RFamide and Hydra-LWamide Preprohormone Genes inHydra:Evidence for Transient Phases of Head Formation

Hydra magnipapillatahas three distinct genes coding for preprohormones A, B, and C, each yielding a characteristic set of Hydra-RFamide (Arg-Phe-NH2) neuropeptides, and a fourth gene coding for a preprohormone that yields various Hydra-LWamide (Leu-Trp-NH2) neuropeptides. Using a whole-mount double-labelingin situhybridization technique, we found that each of the four genes is specifically expressed in a different subset of neurons in the ectoderm of adultHydra.The preprohormone A gene is expressed in neurons of the tentacles, hypostome (a region between tentacles and mouth opening), upper gastric region, and peduncle (an area just above the foot). The preprohormone B gene is exclusively expressed in neurons of the hypostome, whereas the preprohormone C gene is exclusively expressed in neurons of the tentacles. The Hydra-LWamide preprohormone gene is expressed in neurons located in all parts ofHydrawith maxima in tentacles, hypostome, and basal disk (foot). Studies on animals regenerating a head showed that the prepro-Hydra-LWamide gene is expressed first, followed by the preprohormone A and subsequently the preprohormone C and the preprohormone B genes. This sequence of events could be explained by a model based on positional values in a morphogen gradient. Our head-regeneration experiments also give support for transient phases of head formation: first tentacle-specific preprohormone C neurons (frequently associated with a small tentacle bud) appear at the center of the regenerating tip, which they are then replaced by hypostome-specific preprohormone B neurons. Thus, the regenerating tip first attains a tentacle-like appearance and only later this tip develops into a hypostome. In a developing bud ofHydra,tentacle-specific preprohormone C neurons and hypostome-specific preprohormone B neurons appear about simultaneously in their correct positions, but during a later phase of head development, additional tentacle-specific preprohormone C neurons appear as a ring at the center of the hypostome and then disappear again. Nerve-freeHydraconsisting of only epithelial cells do not express the preprohormone A, B, or C or the LWamide preprohormone genes. These animals, however, have a normal phenotype, showing that the preprohormone A, B, and C and the LWamide genes are not essential for the basic pattern formation ofHydra.

Functional Organization of Dermal Coelomic Canals in Sipunculus nudus (Sipuncula) with a Discussion of Respiratory Designs in Sipunculans

Sipunculus nudus is a large sipunculan that burrows actively in porous marine sands. The body surface is folded into approximately 30 longitudinal ridges that extend along the length of the trunk and introvert. A dermal canal lies beneath each of the ridges and circulates coelomic fluid and hemerythrocytes to within a few micrometers of the body surface. Coelomic fluid enters and leaves the dermal canals through pores leading from the trunk coelom and flows unidirectionally at approximatey 0.7 mm/s from posterior to anterior. The flow is gen- erated by cilia on peritoneal cells lining the canals. The volume of the canals is approximately 8% of the total coelomic volume. We suggest that sipunculan species fall into three functional categories based on the body region or regions used for environmental gas exchange. Tentacle breathers, such as species of Themiste, bore into rocks or micro-oxic sediments and extend their numerous tentacles into the water. Dissolved gases are transported between the tentacular and trunk coelomic cavities via well-developed contractile vessels. Tentacle and introvert breathers, such as species of Aspidosiphonidae and Phascolosomatidae, lodge the trunk region of the body in the substratum and extend an elongated, thin-walled introvert and tentacles into the water. Their contractile vessels are usually simple unbranched tubes. Integumentary breathers, such as Sipunculus nudus and other species of Sipunculidae, have integumentary specializations for gas exchange across the entire body surface, but usually small tentacles and often weakly developed con- tractile vessels.

A Note on the British Species of Cucumarians, Involving the Erection of Two New Nominal Genera

While preparing a report on Echinodermata from the Stilly Isles, based on collections made by the University of London Sub-Aqua Club but including also earlier records by various authors (F. W. E. Rowe,J. nat. Hist., in the Press), it became apparent that the species generally known asCucumaria saxicolaBrady & Robertson andC. normaniPace, from Mortensen's classic handbook (1927), have not been satisfactorily reassigned generically since the break-up ofCucumaria sensu extensoand need new generic names in conformity with current views on generic distinctions in the Dendrochirotida.Mortensen (1927), in his survey of the Echinoderms of the British Isles, includes seven species in the genusCucumaria: C. frondosa(Gunnerus);C. elongataDüben & Koren;C. hyndmanniThompson;C. saxicolaBrady & Robertson;C. normaniPace;C. lactea(Forbes) andC. planci(Brandt), this last species being wrongly credited to von Marenzeller.C. frondosais a plump to barrel-shaped animal with ten large, bushy tentacles, podia, at least in the older specimens, not restricted to the ambulacral areas, a calcareous ring with no posterior bifurcations on the radial plates or any fusion of the ventralmost radial and adjacent interradial plates and spicules of the body wall comprising thin, multilocular, smooth or slightly thorny plates, these being more or less restricted to the posterior region and to the podia in older animals. It has been designated type-species of the genus by Panning (1949), thus delimitingCucumaria sensu stricto. The other species included by Mortensen cannot be treated as being congeneric withfrondosaby virtue of their elongate body, ten relatively small tentacles of which the ventralmost two are smaller than the remaining eight, podia restricted to the ambulacral areas, calcareous ring showing a tendency, in some forms, to develop posterior bifurcations on the radial plates and fusion of the ventral-most radial and adjacent interradial plates and the differing form and combinations of spicules of the body wall.

OBSERVATIONS OF THE FEEDING MECHANISM OF A CTENOPHORE,MNEMIOPSIS LEIDYI

The mode of feeding was studied in young tentacled forms and in the adult Mnemiopsis leidyi. The young capture food with their branched tentacles, and deposit it in the mouth. The adults entangle the food with the small tentacles along the tentacular ridge, and deposit it in the labial trough, whence it is carried to the mouth. Food enters the stomodæum and after digestion is cast out of the mouth, or it may enter the food canals and pass out of the anus.